1. Technical Field
The invention relates to re-closable cartons of folded paperboard or other laminar material, such as are used for storing and dispensing soap powder, detergent and like powdered or granular materials; and to blanks for making such cartons.
2. Background Art
Cartons for granular or powdered material, for example detergents, usually are made by die-cutting and creasing a blank of paperboard or the like to define front, rear and side panels and top and bottom flaps. The blank is partially folded but shipped and stored flat. Prior to filling, the sides are folded at the creases to form a rectangular tube and the flaps at one end are folded and glued to form an open box. Once filled, the flaps at the other end are folded and glued to seal the carton and keep its contents dry.
Some early designs of carton had tear lines defining a tab which the user would force inwards to rupture the tear lines and make an opening through which to pour the detergent. The user could tear back the end of the carton top in order to obtain faster flow. A disadvantage of such cartons is that they did not re-close properly and did not provide good access for a scoop to dispense the detergent.
More recently, cartons have been provided with "tear strips" to make them easier to open. Typically, a pair of parallel slits in the exterior surfaces of the front and side walls define between them a "tear strip" of paperboard a short distance below the top edge of the carton. An internal plastic strip underlying the strip of paperboard has one end protruding to enable a user to grasp and pull it to tear away the tear strip. The portion of the carton above the tear strip forms a hinged lid which remains attached to the rear wall and hinges about the upper rear corner. A disadvantage of such cartons is that they can only be filled to the level of the bottom of the tear strip, which wastes space and incurs unnecessary costs.
It is known to overcome the problem of reduced fill level by providing a liner in the form of a rectangular paperboard tube which is the full height of the carton, as disclosed in U.S. Pat. No. 5,058,748 (Giblin et al) issued Oct. 22, 1991. After the tear strip has been removed and the top hinged open, the liner protrudes above the torn edges of the front and side walls allowing the carton to be filled to capacity.
U.S. Pat. No. 5,161,734 (Ruehl et al) discloses an alternative solution which provides double-layer front and side panels. The tear strip is provided in the outer layers of the front and side panels. When the tear strip is removed, the top panel and portions of the front and side panels depending from it form a lid which hinges open about the top crease of the rear panel. The inner layers remain the full height ensuring maximum fill level. In order to provide a positive locking arrangement to retain the lid when reclosed, despite repeated opening and closing of the carton, Ruehi et al's carton has a locking tab formed depending from the inner front layer to engage a flap adhered to that portion of the outer layer which, when the carton is opened, remains attached to the lid. When the carton is re-closed, the strip engages the lower edge of the locking tab and retains the carton closed. A disadvantage of such known cartons is that the use of liners or double-layer panels, and separate tear strips, increases material and production costs.
U.S. Pat. No. 4,289,240 (Mueller) issued Sep. 15, 1981, discloses a flip-lock re-closable carton having a receptacle portion and a hinged cover portion. An extension flap is adhered to the front panel of the carton and splits away from a depending front flap of the cover as the cover is initially opened by a user. A portion of the extension flap remains hingedly attached to the front flap and forms a locking tab which engages in the void from which it was removed to provide a locking action on reclosure. While this carton avoids the expense of a separate, disposable tear strip, it is not entirely satisfactory because its configuration is such that it requires complex machine assembly. Also, none of the above-described cartons has a locking arrangement which can be readily applied to both the front and sides of the carton.